Occupant restraint air bag

Abstract: An occupant restraint air bag assembly (10) includes an air bag (22) having a base wall portion communicating with an inflator (16) and an occupant contacting face wall (32) for contact with the occupant (14) upon inflation of the bag. The air bag (22) also has an internal dividing wall (30) which divides the air bag (22) into a first chamber (26) communicating directly with the inflator (16) and a second chamber (28) defined between the dividing wall (30) and the occupant contacting face wall (32). A first opening (36) in the dividing wall (32) between the chambers (26,28) communicates inflation gas from the first chamber (26) to the second chamber (28) to inflate the second chamber (28). A second opening (38) in the dividing wall (30) is normally closed by a vent flap (44) which is operably connected to the occupant contacting face wall (32) so that the inflation of the second chamber (28) and resultant travel of the face wall (32) towards the occupant (14) and away from the dividing wall (30) will move the valve flap (44) to an open position by which the inflation gas is communicated into the second chamber (28) through both the first opening (36) and the second opening (38) during the further inflation of the bag (22).

Description: The present invention relates to an occupant restraint air bag which includes two chambers with a valve communicating inflation gas between the chambers. It is well known to provide an inflatable air bag for restraining a vehicle occupant. The air bag assembly includes a folded bag which is connected to a source of inflation gas. Release of the inflation gas into the air bag causes the bag to expand rapidly so that a face wall of the air bag is displaced towards contact with the occupant. It is known to provide such air bags having internal walls which divide the air bag into various chambers and to provide openings in the walls to communicate inflation gas between the chambers. Various arrangements of check valves and pressure relief valves have been proposed for selectively opening and closing the opening to control the communication of inflation gas between the chambers. US-A-3586347 describes a system in accordance with the preamble of claim 1. DE-A-3618060 describes an air bag system having a release vent opened by a cord. The present invention seeks to provide an improved air bag. An occupant restraint air bag in accordance with the present invention is characterised over US-A-3586347 by the features specified in the characterising portion of claim 1. The degree of opening and closing of the second opening between the air bag chambers is dependant upon the displacement of the air bag towards the fully deployed position. Preferably, there is provided an air bag assembly which includes an air bag having a base wall portion communicating with an inflator providing inflation gas and an occupant contacting face wall for contacting the occupant upon inflation of the bag. The air bag preferably has an internal dividing wall which divides the air bag into a first chamber communicating directly with the inflator and a second chamber defined between the dividing wall and the occupant contacting face wall. A first opening in the dividing wall between the chambers can permit the controlled communication of inflation gas from the first chamber to the second chamber to inflate the second chamber. A second opening in the dividing wall is preferably normally closed by a vent flap which is operably connected to the occupant contacting face wall so that the inflation of the second chamber and resultant travel of the face wall towards the occupant and away from the dividing wall will move the valve flap to an open position by which the inflation gas is communicated into the second chamber through both the first opening and the second opening during the further inflation of the bag. A travel limiting tether is preferably attached to the dividing wall to limit the displacement of the dividing wall and consistently establish the position of the second opening and valve flap. The valve flap is preferably connected to the face wall by a tether of predetermined length chosen to cause the opening of the second opening when the travel of the face wall towards the occupant has progressed to a predetermined degree of the total travel of the occupant face panel. Advantageously, there is provided a multi-chambered air bag having valving to control the flow of inflation gas between the chambers in response to the degree of inflation of the air bag. In a preferred embodiment, there is provided an air bag divided into a chamber closest the inflator and a chamber closest the occupant, with openings and valving acting between the chambers in a manner to limit the size of the flow opening until an occupant contacting wall of the air bag has moved away from the inflator by a predetermined distance towards the occupant. An embodiment of the present invention is described below, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a cross-sectional view of an embodiment of air bag and showing in schematic form the inflation of the air bag in which limited travel of the air bag occurs; Figure 2 is a view similar to Figure 1 showing the further inflation of the air bag towards an occupant seated further from the module; Figure 3 is a perspective view of the air bag of Figure 1 showing the construction in greater detail; and Figure 4 is a view similar to Figure 3 of a second embodiment of air bag. Referring to Figure 1, the embodiment of air bag module 10 shown is mounted in a recess in the top surface of an instrument panel 12 located in front of an occupant 14. The air bag module 10 includes an inflator 16 which generates inflation gas and is mounted in a housing or canister 18. An air bag 22 of flexible fabric material is suitably mounted on the module 10 and is normally folded upon itself to overlie the inflator 16 in a stored condition beneath the outer surface of the instrument panel. Figure 1 shows the air bag 22 having been unfolded and deployed through the instrument panel towards the occupant by inflation gas upon activation of the inflator 16. As best seen in Figure 2 the air bag 22 is divided into a first chamber 26 and a second chamber 28 by a vertical (in the view shown) dividing wall 30. The first chamber 26 communicates directly with the inflator 16 to receive the inflation gas therefrom, while the second chamber 28 is separated from the inflator 16 by the dividing wall 30. The second chamber 28 is situated between the dividing wall 30 and a occupant contacting face wall 32 of the air bag 22. A travel limiting tether strap 34 has one end attached to the inflator 16 and the other end attached to the dividing wall 30 and functions to limit the travel of the dividing wall 30 towards the occupant so that the dividing wall 30 attains the vertical position of Figure 2 against the forces of the inflation gas acting thereon. The dividing wall 30 has a first opening 36 provided therein which communicates inflation gas from the first chamber 26 to the second chamber 28. In addition, the dividing wall has a second opening 38 therein provided with a open mesh screen 40. In Figure 1 it can be seen that the second opening 38 provided by the open mesh screen 40 is closed by a valve flap 44 which reaches through the first opening 36 and overlies the upstream side of the second opening 38 to block the flow of inflation gas through the open mesh screen 40. As best seen in Figure 2, the valve flap 44 has an end 46 sewn or otherwise suitably attached to the occupant contacting face wall 32 so that the travel of the occupant contacting face wall 32 to the position of Figure 2 pulls the valve flap 44 away from the second opening 38 so that the inflation gas is free to pass from the first chamber 26 to the second chamber 28 through both the first opening 36 and the second opening 38. Thus, the valve flap 44 and the second opening 38 cooperate to form a closure which is initially normally closed to block the passage of gas therethrough but then opens to permit the passage of gas. Figure 3 is a perspective view of the air bag shown in the fully inflated position of Figure 2 and having parts broken away and in cross-section to show in greater detail the construction of the air bag 22. As best seen in Figure 3 the travel limiting tether strap 34 is preferably formed of a piece of air bag-type fabric which includes laterally spaced legs 50 and 52 which are sewn or otherwise suitably attached to the dividing wall 30 at laterally spaced locations to support the dividing wall 30 at its vertical position of Figures 1 and 2. Furthermore, Figure 3 shows that the first opening 36 is preferably a round opening which is situated beneath and centred with respect to the second opening 38. In the pre-deployment folded condition, the valve flap 44 will reach through the first opening 36 and be unfolded to overlie the open mesh screen 40 of the second opening 38. The edges of the valve flap 44 are preferably tacked to the vertical wall 30 by a row of stitches, adhesive, velcro or other suitable fastener which can be forcibly separated when the valve flap 44 is to be moved away from the second opening 38. Furthermore, as best seen in Figure 3 the valve flap 44 includes a waisted tether portion 54 which enables the valve flap 44 to pass through the opening 36 without substantially reducing the flow area of the first opening 36. In comparing Figure 1 and Figure 2, it will be appreciated that the length of the valve flap 44 and/or its tether 54 may be varied as desired to determine the degree of movement of the occupant face wall 32 away from the dividing wall 30 which will result in the valve flap 44 being tensioned and pulled through the first opening 36 to open the second opening 38. Furthermore, it will be appreciated that the tether 44 has a predetermined length chosen to cause opening of the closure when the travel of the face wall 32 towards the occupant has progressed to a predetermined degree of the total travel of the face wall 32 so that the further inflation of the second chamber 28 is obtained by the combined communication of inflation gas through both the first opening 36 and the second opening 38, and to cause the closure to remain closed during any degree of lesser progress of the face wall 32 so that the inflation of the second chamber 28 is obtained only by inflation gas communication through the first opening 36. Figure 4 shows an alternative embodiment of air bag 60 which has a vertical (in the view shown) dividing wall 62 having a plurality of first openings 64 spaced circumferentially about the secondary opening 66. The open mesh screen 68 which extends across the opening 66 stops short at the top thereof to leave a gap 70 through which the valve flap 74 reaches to overlie the open mesh screen 66. The aggregate area of the first openings 64 will control and limit the flow of inflation gas from the first chamber to the second chamber until such time as the travel of the occupant contacting face wall 76 has progressed away from the dividing wall 62 sufficiently to pull the movable flap 74 out of closing engagement with the open mesh screen 68 of the second opening 66. It will be appreciated that the use of the multi-chamber arrangement disclosed herein, and the displacement responsive valving arrangement for the dividing wall between the chambers permits the tuning of the air bag system to a wide range of desired performance characteristics. For example the size, shape, number and spacing of the vent openings may be varied. In addition, the length of the valve flap and its tether portion may be varied to vary the degree of movement of the occupant contact face wall which triggers the opening of the valve flap. In addition, the material of the valve flap can be chosen to be either a gas permeable or impermeable material. Furthermore, although the drawings herein show an air bag formed of two chambers it will be appreciated that three, four or any number of chambers may be used and may have associated primary flow openings which are open and secondary normally closed flow openings which are opened by a valve in response to the relative displacement between different wall portions of the air bag. In addition, it will be understood that the addition of a dividing wall in the air bag is only one example of how the separate chambers may be fabricated. Alternately, two chambers could be achieved by using a smaller complete bag within the larger complete bag, each having top, bottom and side walls so that the inner smaller bag would provide the dividing wall between the chambers. The valve arrangement described here could then be utilised in a similar fashion. In addition it will be appreciated that the particular closure valve arrangement shown herein is just one example of suitable valve arrangement which may be installed in the dividing wall. Although the valve flap preferably reaches through an access opening such as the first opening 36 of Figure 3, or the gap 70 of Figure 4, it will be appreciated that the valve flap could close the secondary opening on the downstream side thereof within the second chamber. Furthermore it will be understood that the valve assembly shown herein is only one example of a suitable valve assembly, and other valve assemblies such as that disclosed in our co-pending European patent application no. 93203176.8 may be employed in the air bag assembly hereof.

Claims: An occupant restraint air bag comprising an inflator (16) for generating inflation gas; an air bag (22) including a first chamber (26) coupled directly with the inflator and a second chamber (28) defined by an occupant contacting face wall (32,76) and separated from the first chamber by a dividing wall (30,62), at least one first opening (36,64) in the dividing wall between the first and second chambers to permit controlled passage of inflation gas from the first chamber to the second chamber, and a second opening (38,66) in the dividing wall between the chambers,characterised by closure means (44,74) normally closing the second opening to passage of inflation gas from the first chamber to the second chamber, and by actuating means (54) located within the second chamber and including a first end operably associated with the closure means and a second end attached to occupant contacting facing wall of the air bag so that the inflation of the second chamber and resulting displacement of the occupant contacting face wall opens the closure means when the occupant contacting face wall has moved by a predetermined amount. An occupant restraint air bag according to claim 1, comprising a tether (34) attached to the dividing wall (30,62) for limiting displacement of the dividing wall. An occupant restraint air bag according to any preceding claim, comprising a mesh screen (40,68) extending across the second opening (38,66). An occupant restraint air bag according to claim 3, wherein the closure means (74) passes through a gap (70) between the second opening (66) and the mesh screen (68). An occupant restraint air bag according to any one of claims 1 to 3, wherein the closure means (44) passes through the first opening (36). An occupant restraint air bag according to any preceding claim, comprising an inner bag, the dividing wall (30) forming part of the inner bag, the first chamber (26) being bounded by the inner bag. An occupant restraint air bag according to any preceding claim, comprising a plurality of first openings (64).

Inventors: JENSEN JACK LEON, MELVIN JOHN WILLIAM, JENSEN, JACK LEON, MELVIN, JOHN WILLIAM
Applicants: GEN MOTORS CORP, GENERAL MOTORS CORPORATION
Application year: 1994
Main classification: B60R21
IPC codes: B60R21